#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "jsmn.h"
/************************************************************************/
/*                                                                      */
/************************************************************************/
/*
 * A small example of jsmn parsing when JSON structure is known and number of
 * tokens is predictable.
 */

 /*
    {
        "user": "johndoe",
        "admin": false,
        "uid": 1000,
        "groups": ["users", "wheel", "audio", "video"]
    }
 */
 
static const char *JSON_STRING =
    "{\"user\": \"johndoe\", \"admin\": false, \"uid\": 1000,\n  "
    "\"groups\": [\"users\", \"wheel\", \"audio\", \"video\"]}";

static int jsoneq(const char *json, jsmntok_t *tok, const char *s) {
  if (tok->type == JSMN_STRING && (int)strlen(s) == tok->end - tok->start &&
      strncmp(json + tok->start, s, tok->end - tok->start) == 0) {
    return 0;
  }
  return -1;
}

/************************************************************************/
/*                                                                      */
/************************************************************************/

int main(int argc, char* argv[])
{
    int i;
    int r;
    jsmn_parser p;
    jsmntok_t t[128]; /* We expect no more than 128 tokens */

    jsmn_init(&p);
    r = jsmn_parse(&p, JSON_STRING, strlen(JSON_STRING), t,
                 sizeof(t) / sizeof(t[0]));
    if (r < 0) {
        printf("Failed to parse JSON: %d\n", r);
        return 1;
    }

    /* Assume the top-level element is an object */
    if (r < 1 || t[0].type != JSMN_OBJECT) {
        printf("Object expected\n");
        return 1;
    }

    /* Loop over all keys of the root object */
    for (i = 1; i < r; i++) {
        if (jsoneq(JSON_STRING, &t[i], "user") == 0) {
          /* We may use strndup() to fetch string value */
          printf("- User: %.*s\n", t[i + 1].end - t[i + 1].start,
                 JSON_STRING + t[i + 1].start);
          i++;
        } else if (jsoneq(JSON_STRING, &t[i], "admin") == 0) {
          /* We may additionally check if the value is either "true" or "false" */
          printf("- Admin: %.*s\n", t[i + 1].end - t[i + 1].start,
                 JSON_STRING + t[i + 1].start);
          i++;
        } else if (jsoneq(JSON_STRING, &t[i], "uid") == 0) {
          /* We may want to do strtol() here to get numeric value */
          printf("- UID: %.*s\n", t[i + 1].end - t[i + 1].start,
                 JSON_STRING + t[i + 1].start);
          i++;
        } else if (jsoneq(JSON_STRING, &t[i], "groups") == 0) {
          int j;
          printf("- Groups:\n");
          if (t[i + 1].type != JSMN_ARRAY) {
            continue; /* We expect groups to be an array of strings */
          }
          for (j = 0; j < t[i + 1].size; j++) {
            jsmntok_t *g = &t[i + j + 2];
            printf("  * %.*s\n", g->end - g->start, JSON_STRING + g->start);
          }
          i += t[i + 1].size + 1;
        } else {
          printf("Unexpected key: %.*s\n", t[i].end - t[i].start,
                 JSON_STRING + t[i].start);
        }
    }

    return 0;
}